Silver halide photographic materials generally comprise a support having thereon at least one light-sensitive silver halide emulsion layer and provided thereon a surface layer, that is, a protective layer comprising hydrophilic colloid materials represented by gelatin. When such photographic materials are stored under high temperature, still further, high temperature and high humidity conditions, such a phenomenon as surfaces of photographic materials are adhered is liable to occur. This adhesion is caused by the contact of photographic materials each other or with other materials in a camera and is generated during production, use or storage of photographic materials and has been a problem.
Further, such adhesion is liable to injure the outer surfaces of photographic materials by contact of photographic materials each other or when photographic materials come into contact with devices of exposure and development processing thereof and, further, causes troubles such as failures by static electricity due to discharge generated by friction or peeling of photographic materials each other or photographic materials with or from the devices.
In addition, another problem arises such that when a photographic material is processed using an automatic processor capable of continuously developing, fixing, washing and drying, transporting property is lowered by the adhesion of a photographic material to the parts in an automatic processor.
Therefore, surface roughening (matting) by incorporating organic or inorganic fine grains (a so-called matting agent) into emulsion layers or the surface protective layer on the back side of the support of a silver halide photographic material is widely conducted for purposes of prevention of the above-described adhesion under high temperature and high humidity conditions, improvements of antistatic property, scratch resistance and transporting property, in addition, improvements of discriminating abilities of the surface side and the back side of a photographic material and vacuum contact at the time of contact exposure. Various sizes of matting agents are used according to purposes but, in general, those having sizes of from 1 .mu.m to 10 .mu.m are preferably used.
Examples of matting agents often used for silver halide photographic materials include inorganic materials such as silicon dioxide, titanium dioxide, magnesium oxide, calcium carbonate, magnesium carbonate, barium sulfate, and strontium sulfate, and fine grain powders of organic materials such as polymethyl acrylate, polymethyl methacrylate, polyacrylonitrile, polystyrene, cellulose acetate, and cellulose acetate propionate. Examples of these matting agents are disclosed in U.S. Pat. No. 3,411,907, British Patent 837,529 and Research Disclosure, Vol. 176, No. 17643 (December, 1978).
However, although the above-described problems are improved by using a matting agent, new problems arise. The above problems are improved using a large amount of a matting agent to increase the matting degree of the surface but the increased amount of a matting agent leads to deteriorations of graininess and transparency of a material.
Many of conventionally used matting agents are broad in grain size distribution, for example, for giving adhesion resistance to a silver halide photographic material, a large quantity of matting agents must be present in a surface protective layer or a backing layer, inclusive of matting agents having grain sizes not necessary. Polymer grains having grain sizes of 1 .mu.m or less are insufficient to impart adhesion resistance to a photographic material and which causes deterioration of haze cutting, therefore, such a matting agent is not desired in a photographic material requiring transparency. Further, polymer grains having grain sizes of 10 .mu.m or more are not preferred as they deteriorate graininess of an image, in addition, such polymer grains have a drawback such that they precipitate in a coating solution or generate agglomerates and make coating difficult. Therefore, such big polymer grains are necessary to be removed as much as possible.
These two points, that is, deteriorations of graininess and transparency, appear markedly when a development processed photographic material containing a matting agent is enlargement printed or projected using a specular light source or copied using the same light source (for example, optical print in the movies).
Moreover, when a large amount of a matting agent is used, an undesired defect is often caused such as micro-holes (pinholes) are dotted on images due to the precipitation of the matting agent. In particular, in a photographic material of forming high contrast images by rapid processing, generation of pinholes is conspicuous when the amount of gelatin binder in the silver halide emulsion layer is reduced to heighten the rapid processability, therefore, the generation of pinholes and the reduction of optical density (blackening density) therefrom cannot be avoided by generally used matting agents having broad grain size distributions. When the amount of gelatin binder is increased to avoid the generation of pinholes, not only drying property is extremely deteriorated but also dimensional stability of a photographic material is reduced.
A technique of improving some of the above problems of antistatic property, transporting property, adhesion resistance, transparency, scratch resistance, graininess, drying property and mat pinholes by using monodispersed polymer grain as a matting agent is disclosed.
The first example of applying monodispersed polymer grains as a matting agent in a silver halide photographic material has been disclosed in Research Disclosure, Vol. 21617, No. 216 (1982). The disclosure has clarified that the use amount of a matting agent necessary to obtain certain frictional resistance can be reduced using monodispersed polymethyl methacrylate grains having an optimal grain size of 1.8 .mu.m, and pinholes and coating defect due to coarse grains can be removed. However, the manufacturing method of the monodispersed matting agent and the monodispersibility (grain size distribution) thereof are not disclosed in the above Research Disclosure.
Further, improving effects of adhesion resistance and antistatic property by polymethyl methacrylate grains having a number-average grain size of from 0.8 to 2.3 .mu.m synthesized by dispersion polymerization are disclosed in JP-B-5-59924 (the term "JP-B" as used herein means an "examined Japanese patent publication"), but many of the grain size distributions of the polymer grains disclosed in the same patents are broad such as from 0.19 to 1.23 in terms of variation coefficient and the improving effect of surface characteristics such as adhesion resistance has been insufficient. Compatibility of adhesion resistance and transparency is disclosed in JP-A-61-230141 (the term "JP-A" as used herein means an "unexamined published Japanese patent application"). In addition to the above patents, monodispersibilities of matting agents are disclosed in JP-A-59-149357, JP-A-60-156056, JP-A-63-8736, JP-A-63-235314, JP-A-1-281443, JP-A-2-54249, JP-A-4-78845, JP-A-5-289225, European Patents 341200, 118793, U.S. Pat. Nos. 4,940,653, 4,614,708 and 4,885,530. Monodispersed polymer grain matting agents disclosed in these patents are clarified to have superior properties to polydispersed matting agents in adhesion resistance, graininess, transporting property, antistatic property and transparency, but these polymer grain matting agents disclosed in the above patents are generally low in monodispersibility and the improving effect of mat pinholes is insufficient.
In recent years, a technique of using polymethyl methacrylate grains having extremely high monodispersibility is disclosed in European Patents 610522 and 618490, and reported that the technique is very effective for improving adhesion resistance and antistatic property.
However, the improving effect of mat pinholes is not yet sufficient and the development of a matting agent having a higher property has been desired.
On the other hand, a technique of incorporating a functional group which forms a covalent bond by reacting with an organic hardening agent or a functional group which forms a covalent bond by reacting with gelatin into a matting agent is disclosed in JP-A-64-52138, but the technique primarily aims to prevent a matting agent from peeling off from a photographic material when a processing solution is squeegeed from a photographic material by a rubber plate or a pair of rollers, and the improvement of mat pinholes could not be achieved by this method. Further, a technique of using a matting agent individually covered with covalently bonded gelatin is disclosed in JP-A-1-158427. According to this technique, after an emulsion layer and an overcoat layer (a protective layer) are cooled, hardened and dried, a matting agent is coated thereon (successive coating) and mat pinholes are improved thereby, further, peeling off of a matting agent is prevented as the matting agent is a matting agent covered with gelatin. The patent discloses that mat pinholes cannot be improved when a matting agent not bonded with gelatin is incorporated into a protective layer and coated simultaneously with an emulsion layer.
The above successive coating has drawbacks such that the manufacturing process is complicated and expensive. Accordingly, a method of improving mat pinholes by simultaneous coating has been desired.
Besides the above-described two patents, some techniques using grains reactive with gelatin are disclosed. Grains having an average grain size of from 0.02 to 0.5 .mu.m comprising polymers reactive with gelatin are disclosed in JP-A-62-141540, but these grains cannot sufficiently mat the surface of a photographic material. The polymer latexes having an active methylene group reactive with gelatin are disclosed in U.S. Pat. Nos. 3,700,456, 4,215,195 and 4,421,915 but these grains also cannot be used for matting the surface of a photographic material because grain sizes are small.